The present invention relates to magnetically actuated information display devices.
Display panels which consist of multiples of discrete segments are widely used for the visual indication of information. Display panels using magnets or electromagnets are known in the art and employ various methods to communicate the information to the viewer. The magnetism applied in such devices causes the change of information presented and also maintains the presentation of the information after the change has occurred. A luminous display device is described in U.S. Pat. No. 3,825,927 to Passien. That invention teaches the use of disks or slugs disposed in a chamber between the poles of an electromagnet. One wall of the chamber contains an opening through which light shines from a light source external to the chamber. By selective amplification of energy to the electromagnet, the disks or slugs may be moved from one position in which they cover the opening in the chamber wall to another position in which the opening in the wall is exposed and light shines around the periphery of the disks or slugs and can be viewed from the exterior of the device through a transparent wall of the chamber. A disadvantage of this arrangement is that it requires a self-contained light source for indication of information and also requires continuous excitation of the electromagnets even after the change of position has been achieved to maintain the disks in position. Thus, the device does not have bipolar stability.
Another display panel is described in U.S. Pat. No. 3,698,793 to Tellerman. This device teaches the use of a viewing panel which includes a light diffusing boundary. An electromagnet is used to press an opaque member against the inner surface of the light diffusing boundary, thereby displaying to the viewer the color of the opaque member. One disadvantage of this device is that the color density displayed to the viewer depends on the relative pressure applied to the opaque member. Furthermore, the sharpness of the image displayed to the viewer may be reduced by irregularities in the contacting surfaces of the opaque member and the light diffusing boundary. This device also requires the continuous application of energy to the electromagnetic elements in order first to change and then to maintain the position of the opaque member. Thus, the device does not have automatic bipolar stability.
Yet another display panel is described in U.S. Pat. No. 3,916,403 to Mandzsu, et al. Mandzsu, et al. teaches a permanent magnet contained in a flip leaf which is pivotally connected to a base panel. The flip leaf has two surfaces, each of a different color. A reversal of the polarization state of a core under the panel causes the flip leaf magnet to be either repelled or attracted depending on the polarity state chosen. This residual magnetism in the core causes the flip leaf to either remain in its present position or to pivot to expose its other surface so as to change the color presented to the viewer. This device achieves bipolar stability as a result of this residual magnetism in the core of the electromagnet. The residual magnetism acts on the permanent magnet contained in the flip leaf so as to maintain the position of the flip leaf without the need for further application of external energy.
The flip leaf of this device is directly exposed to the viewer rather than being contained within a sealed chamber having a viewing panel. This display panel has the disadvantage of increased frictional wear on the colored surfaces of the flip leaf and on the pivot points of the flip leaf. Such wear may result in the loss of colored areas thereby reducing the quality of the information displayed. Such wear may ultimately result in the complete detachment of the flip leaf from its base panel.
Another display panel known in the art is described in U.S. Pat. No. 3,812,490 to Goodrich. This device teaches a flexible membrane impregnated with magnetic particles. A plurality of electromagnetic elements are energized to produce a desired polarity so as to selectively repel or attract the flexible membrane. The visibility of the outer surface of the flexible membrane in Goodrich is a function of its proximity to a transparent window. When the membrane is attracted to the electromagnetic elements, the opaque fluid of the chamber is present between the flexible membrane and the window, thereby preventing visualization of the membrane's surface from the exterior of the device. When the flexible member is repelled by the electromagnetic elements, the membrane is at least partially in contact with the inner surface of the window and can be seen from the exterior of the device. This device is bistable in that energy needs to be applied to a selected electromagnetic element only while changing the polarity of the electromagnetic element.
The Goodrich device has the disadvantage of producing an image to the viewer which may lack clarity or create a variance in color or color density and produce a fuzzy image. This is because the flexible membrane is continuous and the polarization of one or more but not all of the electromagnetic elements will result in a variation in proximity to the window of the various areas of the membrane. The portion of the flexible membrane over non-energized electromagnetic elements is furthest from the window whereas the portion of the membrane over energized elements is pressed into contact with the window. Between these two portions is an area of the membrane having intermediate proximity to the window. Since this membrane area is also in tension, there is a tendency for it to pull away from contact with the window when adjacent elements are not also repelling the membrane, thereby creating uneven contact of the membrane, and thus a poor quality image.
Yet another information display apparatus that is known in the art is a device which includes a display member mounted in a chamber containing an opaque fluid of a color that is in contrast with the color of the surface of the display member. The display member is seen through a transparent viewing face of the chamber when it is positioned in face-to-face contact with the transparent window. An elongated spigot is affixed to the rear of the display member. It includes a permanent magnet and slides in and out of an elongated recess formed from, and continuous with, the chamber. A coil surrounds the recess and, when energized, interacts with the permanent magnet of the spigot to produce either a repelling or an attracting force to move the spigot within the recess.
The movement of the spigot in this apparatus depends on the continued application of electrical energy to the coil surrounding the recess of the chamber. This is because the apparatus does not teach a stationary core within the coil which can be selectively polarized in one of two states upon energization of the coil. Absent such a core, there can be no retention of an amount of residual magnetism after de-energization of the coil sufficient to drive the spigot to completion of its movement into either proximity with the transparent viewing face or with the rear face of the chamber, depending on the polarity of magnetism of such a core.
This type of device can be bistable, since the position of the display element can be maintained through the existence of surface tension, cohesion, or frictional forces between the face of the display member and the face of either the viewing face or the rear face of the chamber, depending on display element position. Position maintenance may also be achieved by the use of ferromagnetic elements disposed adjacent the recess which are attracted by either pole of the permanent magnet contained within the spigot. This involves only attractive forces.
This device has the disadvantage that it is a more complicated chamber structure, which increases manufacturing costs and decreases the ease of manufacturing. It also employs a less reliable means for achieving bipolar stability and may allow a variance in operational certainty in that the movable core defined by the spigot is subject to frictional or vibrational forces that may restrict or retard its movement.
It is evident from the above that while each of the described display devices relies on magnetism or electromagnetism for its operation, each has disadvantages which have not been overcome in a single device. Such disadvantages include the need to couple energy to each display element at least until travel has been completed, which causes slowness of operation and higher power needs, a dependence on a mechanical pivot that may wear out, a lack of bipolar position stability in the absence of power, a lack of high resolution of the displayed image, and a complexity of structure.
Accordingly, it is an object of the present invention to provide an improved means for displaying information and for changing the information so displayed.
It is another object of the present invention to minimize the duration and magnitude of energy that must be applied in order to initiate a change in the display of information.
It is a further object of this invention to provide for the retention of displayed information without the need for application of electrical energy to the device.
It is another object of the invention to minimize frictional interaction between mechanical components or surfaces in the display device.
It is yet another object of this invention to make possible the use of the display at any mounting angle.
It is yet another object of the invention to provide improved resolution of the displayed image.
It is a further object of the present invention to reduce the cost and to increase the ease of manufacturing of the device by the use of fewer materials, by reducing the size of the device, and by reducing the complexity of the structure of the device.